Air cleaners are normally used with internal combustion engines in off-road equipment, such as tractors, bulldozers and the like, to filter the air before it is drawn into the engine. With the use of off-road equipment, the air being drawn to the engine can contain substantial quantities of solid particles or dust, and it is desirable to separate the larger size dust particles from the air before the air is passed through the filter in the air cleaner in order to prevent premature clogging of the filter.
U.S. Pat. Nos. 3,319,404 and 3,429,108, show air cleaner constructions in which the air being drawn into the cleaner is initially swirled outwardly against the inner surface of the cleaner housing which serves to separate the larger solid particles or dust from the air stream. The air then flows through a central filter to the engine, while the separated particles are passed through an outlet tube in the lower end of the housing and are collected in a flexible rubber-like dust-dumping valve.
The valves, as disclosed in the aforementioned patents, are designed to collect and intermittently dump the dust. In general, the valves are constructed with an upper generally cylindrical portion, which acts as a trap to collect the dust, and the cylindrical portion terminates in a pair of lower lips which seal together under the influence of the engine vacuum.
With valves of this type, the weight of the dust collected in the trap, along with the engine vibration will intermittently cause the lips to open to dump or discharge a portion of the dust in the trap. On termination of engine operation, the weight of the dust will cause the lips to open to discharge the entire quantity of collected dust from the trap.
The lip-type dumping valves as used in the past have certain disadvantages. As the valves are normally installed in an exposed location, and as they are formed out of flexible rubber-like material, they are frequently subjected to damage. In addition, the continual exposure to weather can cause rapid deterioration of the rubber-like material.
It has also been found that the lip-type valves do not completely seal under the influence of the engine vacuum, with the result that small amounts of air are drawn through the valve into the air cleaner and this decreases the efficiency of the dust collection.